The present invention relates to a process for the automatic production of ornamental link chains.
More precisely, the invention relates to a process for the automatic production of a kind of chain known in the field of precious and non-precious jewelry by the term "partridge's eye". Such chains, as it is known, are composed of a series of links, flattened and twisted with respect to a common lying plane, each link being formed by two link members having the shape of one turn of a spiral, with the respective end portions crossed and engaged with each other so that the ends of the terminal parts of one contact the internal profile of the other. In the attached FIG. 1, the kind of chain above identified is shown at the end of its production cycle and before the surface finishing operations. In FIG. 2 the same kind of chain is shown as it appears after one of the possible surface finishing treatments.
The present invention relates moreover to an apparatus for the automatic production of the above described type of chain and operating according to the process subject of the invention.
The ornamental link chains of the kind "partridge's eye" have been produced up to now exclusively by manual techniques. According to these techniques slightly open spires are firstly prepared from wire-like material obtained in various ways, and these are attached in sequence to each other, thus obtaining a rough specimen of a continuous chain having a limited length. The single turns, or link elements, linked to each other, are then deformed by exertion, using a suitable tool, of pressure on the "belly" of each one, i.e. in a direction at right angles to the axis of the chain, so that the two terminal ends of each turn cross each other beyond the halfway point of the turn itself. The shaping of the link is then carried out by placing the turns opposite each other two-by-two, and precisely by rotating alternating turns through 180.degree. over the average plane of the chain, so that after said rotation in each link the ends of the crossed portions of one is in contact with the internal profile of the other. Then the hand-performed welding of the overlapping points of the link elements in each link is carried out. The chain thus obtained has a very irregular contour, because it is prepared with links of the flat kind, and consequently it tends to rotate around its own axis, whereas in order to obtain a uniform product it is necessary that the links be of the twisted type. Said twisting of the ends of the links is performed by blocking one end of the chain on a chuck and the other with a fixed vice. The rotation of the chuck causes the twisting of the ends of the links which is necessary in order to obtain a uniform product.
From the above it results clearly that the manual production process for this kind of chain is extremely fatiguing, stressing for the operator and requires appreciable precision and skill. Moreover, owing to the extreme weakness of the coupling of the chain before the welding thereof, the risk of the chain coming apart is very high, even if it is produced in limited lengths. This constitutes a further inconvenience from the production point of view.